1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier, a printer, a facsimile machine or similar image forming apparatus, and methods used therein, in which images are formed and in which a quality of the images are controlled. More particularly, the invention relates to an image forming condition controlling method and device for use in the image forming apparatus.
2. Discussion of Background
For a conventional image forming apparatus, adjustments are often made to alter the performance conditions of selected processing devices, such as a photoconductive drum, a charger, an exposing unit, a developing device, a transfer device and so on, so as to maintain an acceptable image quality. The adjustment is often necessitated by the photoconductive drum or developer, for example, changing their characteristic performance conditions as a result of aging, repeated use, and operating environment.
In order to adjust the condition of such processing devices, an operation of the respective processing devices is controlled in response to a detected surface voltage of the photoconductive drum and a detected toner density. The adjustment is conventionally performed during a warm-up interval, after a power source switch for the image forming apparatus is turned on.
For example, Japanese Laid-open patent No. 5-45982 describes an image forming condition control device in which the adjustments are performed when the power source switch is turned on and temperature of a fixing roller is not more than a predetermined temperature.
However, as recognized by the present inventor, if the power source switch remains on for more than 24 hours, a considerable performance degradation may be experienced. Because an image condition correction event (i.e. a toggling of the power switch) had not been performed during this interval, the condition of the image forming components continues to degrade to perhaps unsatisfactory levels, which in turn causes the image quality to become increasingly poor.